The present invention relates to ophthalmology, and more particularly to a novel method and instrument for facilitating controlled and precise implantation of an intraocular lens into the posterior chamber of an eye.
Over the last several years, it has become increasingly evident that implantation of posterior chamber intraocular lenses provides many advantages over implantation of anterior chamber lenses in patients who have had a cataractous lens removed by extracapsular extraction methods. While there are many different forms and models of posterior chamber lenses, most generally embody a lens having a plano-convex form which includes a pair of circular open-loops. Each loop extends from an attachment point on the periphery of the lens and has a free end. Generally, posterior chamber lenses include a pair of these loops, called "C" loops, "J" loops, etc., depending on their form. Suffice it to say that posterior chamber lenses have circular open-loops laterally-opposed which extend from the lens body for stabilizing and orienting the lens in the posterior chamber, or when the lens is in the "bag" (the membrane which remains after the cataractous lens has been removed).
While posterior chamber lenses provide certain advantages once they are implanted, it should be recognized that the actual implantation procedure is very difficult because of the minuteness of the eye. The basic problem resides in that the circular open-loops are dimensioned so that the greatest distance between them is significantly larger than the pupil opening--even when the pupil is dilated during surgery--thereby making it very difficult to insert the lens. Generally, a surgeon will grip either the lens or a first one of the loops (the superior loop) with a forceps and insert the other loop downwardly through the corneolimbus and the pupil opening. However, because the pupil opening is small, relative to the distance between the loops, the surgeon must then use some other type of tool to compress the superior loop toward the lens body in order that it may be slipped under the iris for affecting positioning of the lens into the posterior chamber. That step is very tricky, and requires great skill, inasmuch as the surgeon must regrasp the lens and use some type of force to compress the loop.
Various proposals have been made for facilitating this step, several of which include providing various configurations such as eyelets or notches on the superior loop which is second to enter the posterior chamber. The notches and eyelets are configured for engaging a specialized tool so that the loop can be pushed or compressed toward the lens. In addition, various types of lenses are provided with holes, adjacent the periphery of the lens body, so that they may be gripped or stabilized by other types of tools: the whole purpose is to provide lens constructions and loops with the capability of being held and repositioned during maneuvering of the lens into the posterior chamber. However, it should be evident that no matter how the lens loop is configured or whether or not the lens body includes holes, the surgeon must go through the following steps: (1) the surgeon must grip the lens and insert one loop into the posterior chamber; (2) the lens must be regripped and the superior loop compressed while the surgeon rotates the lens inwardly.
While a skillful surgeon may accomplish the above steps, a very considerable problem is presented when the loop is compressed as described above. During the compression step, which is necessary in order for the superior loop to be pressed down behind the iris, the other loop inadvertently may be pushed too hard against the "bag," thereby breaking same which completely destroys the bag's ability to provide support for the lens. The problem is critical, and is compounded by the fact that as the surgeon rotates the lens into position, the pressure exerted against the lens continuously presents the risk of breaking the bag.
Accordingly, it is a general object of the present invention to provide an ophthalmological method for facilitating controlled and precise insertion during implantation of an intraocular lens into the posterior chamber of an eye. The present invention contemplates that the posterior chamber lens will include a pair of circular open-loops, and utilizes the concept of elastically deforming a first one of the loops from its normally nonstressed arcuate shape until it is substantially straight, whereby it is biased into a stressed condition. This is accomplished by providing a novel instrument which includes a tubular member or needle which receives the loop and straightens it into the aforementioned stressed condition. Then, continuing on with the method of the present invention, the other loop is at least partially inserted into the posterior chamber and the straightened or captured loop is pushed outwardly through the tubular member whereby it is rotatably displaced into the posterior chamber. The rotatable displacement is accomplished by, in effect, releasing the loop from its stressed condition.
The above method is very simple, can be practiced very readily and ensures controlled and precise positioning or insertion of the intraocular lens into the posterior chamber. No regripping, or regrasping or compression of a loop is required, and the intraocular lens is automatically rotated into precise position.
Another object of the present invention is to provide an instrument, as described above, which is relatively simple in construction and which will permit ease of handling by a surgeon and enable the controlled insertion. To this end, the present invention contemplates that the instrument includes a holder for gripping by the surgeon. The tubular member extends from the holder and is dimensioned with a length and internal diameter suitable for receiving the loop and deforming it elastically into a substantially straight configuration.
It is another object of the present invention to provide an instrument, as described above, in which there is a displacement means, preferably in the form of a plunger element, which is coaxially mounted and movable within the tubular member selectively operable for displacing the loop away or outwardly from the tubular member so that the stored energy in the loop which causes the loop to reassume its arcuate shape will cause the lens to rotate as it is being implanted into the posterior chamber.
Still another object of the present invention is to provide an instrument, as described above, in which the tubular member is defined by an assembly which includes a first outer cannula within which is coaxially mounted a second inner cannula to define an intermediate and elongate annular chamber for transferring irrigation fluid into the eye. The advantage of that construction is that the integrity of the anterior chamber can be maintained, by the irrigation fluid, during the implantation procedure.
These and additional objects and advantages of the method and instrument of the present invention will be more readily understood after a consideration of the drawings and the following detailed description of the preferred embodiment.